Microstructure and magnetic susceptibility of as-cast Zr-Mo alloys

Suyalatu, Naoyuki Nomura, Kei Oya, Yuko Tanaka, Ryota Kondo, Hisashi Doi, Yusuke Tsutsumi, Takao Hanawa

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The microstructures and magnetic susceptibilities of Zr-Mo alloys were investigated to develop a Zr alloy with a low magnetic susceptibility for magnetic resonance imaging (MRI). The microstructure was evaluated with an X-ray diffractometer (XRD), an optical microscope (OM) and a transmission electron microscope (TEM), and the magnetic susceptibility was measured with a magnetic susceptibility balance. The α′ phase with acicular structure was dominant in Zr-1Mo alloys, while the ω and β phases with the equiaxed and relatively flat (no acicular) microstructure was dominant in Zr-3Mo. The mixed microstructural features of Zr-1Mo and Zr-3Mo were observed in Zr-2Mo, which consists of the α′, ω and β phases. The β phase is stabilized when the Mo content exceeds over 3 mass% Mo. As-cast Zr-Mo alloys showed a minimum value of magnetic susceptibility at 3 mass% Mo, and the value abruptly increased up to 10% Mo before remaining stable up to 15 mass% Mo. XRD, OM and TEM revealed that the minimum value of the susceptibility was closely related to the appearance of the athermal ω phase in the β phase. As the Mo content decreases from 3 mass%, the α′ phase appears with the ω and β phases. On the other hand, as the Mo content increases from 3 mass%, the β phase increases and the ω phase decreases. Thus the appearance of the α′ and β phase leads to an increase in magnetic susceptibility. The magnetic susceptibility of as-cast Zr-3Mo alloy was almost one-third that of Ti-6Al-4V, which is commonly used for medical implant devices. Zr-Mo alloys are useful for medical devices used under MRI.

Original languageEnglish
Pages (from-to)1033-1038
Number of pages6
JournalActa Biomaterialia
Issue number3
Publication statusPublished - 2010 Mar


  • Magnetic susceptibility
  • Zr-Mo alloy
  • α′ Phase
  • β Phase
  • ω Phase


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